Overstock's shares at last check surged 15% to $79.81.
TZero Markets got clearance from the Financial Industry Regulatory Authority to offer its customers retail brokerage services for digital securities.
The tZero unit of Overstock also can provide issuers with investment-banking and placement-agent services when they raise capital.
“Through tZero Markets, we will establish a direct relationship with our customers, while also offering a streamlined experience for onboarding and trading digital securities," tZero Chief Executive Saum Noursalehi said in an emailed statement.
"We expect tZero Markets to launch its services in a couple of months."
At launch, the company said, tZero Markets will start onboarding U.S.-based retail investors with plans to expand to entities and international investors.
Noursalehi added that this was an important milestone to create an innovative marketplace for private assets.
In June Overstock's share price surged after the Midvale, Utah, internet shopping giant reported that tZero handled a record 423,000 transactions in May, four times the volume for the year-earlier period.
In May, tZero said it added two new subscribers: broker-dealers ChoiceTrade and a publicly traded multinational investment bank and financial-services company focused on institutional brokerage on the tZero alternative trading system.
These broker-dealers joined Dinosaur Financial Group as subscribers to the tZero ATS.
Finra, Washington, is a government-authorized not-for-profit organization that oversees U.S. broker-dealers.